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[PG17] Add the ability to do not flush dirty buffers when checkpointing #859

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[PG17] Add the ability to do not flush dirty buffers when checkpointing #859

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15 changes: 13 additions & 2 deletions src/backend/access/transam/xlog.c
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Original file line number Diff line number Diff line change
Expand Up @@ -153,6 +153,9 @@ set_lwlsn_db_hook_type set_lwlsn_db_hook = NULL;
set_lwlsn_relation_hook_type set_lwlsn_relation_hook = NULL;
set_max_lwlsn_hook_type set_max_lwlsn_hook = NULL;

/* NEON: Hook to control checkpoint buffer flushing */
checkpoint_buffers_hook_type checkpoint_buffers_hook = NULL;

/*
* Number of WAL insertion locks to use. A higher value allows more insertions
* to happen concurrently, but adds some CPU overhead to flushing the WAL,
Expand Down Expand Up @@ -7685,7 +7688,10 @@ PreCheckPointGuts(int flags)
if (flags & (CHECKPOINT_IS_SHUTDOWN|CHECKPOINT_END_OF_RECOVERY))
{
CheckPointReplicationState(flags);
CheckPointBuffers(flags);

/* NEON: Allow extension to control checkpoint buffer flushing */
if (!checkpoint_buffers_hook || checkpoint_buffers_hook())
CheckPointBuffers(flags);

/*
* pgstat_write_statsfile will be called later by before_shmem_exit() hook, but by then it's too late
Expand Down Expand Up @@ -7721,8 +7727,13 @@ CheckPointGuts(XLogRecPtr checkPointRedo, int flags)
* wallog FSM/VM pages to persist them at page server.
* Writing to the WAL during shutdown checkpoint cause Postgres panic.
* So do it before in PreCheckPointGuts.
*
* The checkpoint_buffers_hook allows extensions (e.g., Neon) to control
* whether buffer flushing should proceed, as bgwriter and buffer eviction
* also handle FSM/VM flushing.
*/
if (!(flags & (CHECKPOINT_IS_SHUTDOWN|CHECKPOINT_END_OF_RECOVERY)))
if ((!(flags & (CHECKPOINT_IS_SHUTDOWN|CHECKPOINT_END_OF_RECOVERY))) &&
(!checkpoint_buffers_hook || checkpoint_buffers_hook()))
CheckPointBuffers(flags);

/* Perform all queued up fsyncs */
Expand Down
4 changes: 4 additions & 0 deletions src/include/access/xlog.h
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Expand Up @@ -288,6 +288,10 @@ extern set_lwlsn_db_hook_type set_lwlsn_db_hook;
extern set_lwlsn_relation_hook_type set_lwlsn_relation_hook;
extern set_max_lwlsn_hook_type set_max_lwlsn_hook;

/* NEON: Hook to control checkpoint buffer flushing */
typedef bool (*checkpoint_buffers_hook_type) (void);
extern checkpoint_buffers_hook_type checkpoint_buffers_hook;

/*
* Routines used by xlogrecovery.c to call back into xlog.c during recovery.
*/
Expand Down